Day 21: HackerRank 30 Days Of Code Solution | Generics

This post explains the HackerRank 30 Days of Code problem Generics step by step: the problem statement, input and output format, constraints, a sample test case and a working solution in Java that you can study and run.

Day 21: Generics

Generic constructs are a very efficient way of reusing your code. In the same way you have parameters for a function, generics parameterize type and allow you to use apply the same interface, class, or method using different data types while still restricting operations to that data type (meaning that you still get strong type checking at compile time).

Generic implementation

public interface List<E> extends Collection<E>
public interface Map<K,V>

The letters enclosed between angle brackets (< and >) are type parameters and, like many things in programming, there is a convention behind them (remember, following conventions help us write clean, readable code!). The letters below are commonly-used generic type parameters:

E - Element
K - Key
V - Value
N - Number
T - Type (e.g.: data type)
S,U,V, etc. These are second, third, and fourth types for when T is already in use.

Aim

Hey CodingHumans today we're discussing Generics; be aware that not all languages support this construct, so fewer languages are enabled for this challenge.

Task

Write a single generic function named printArray; this function must take an array of generic elements as a parameter (the exception to this is C++, which takes a vector). The locked Solution class in your editor tests your function.

Note: You must use generics to solve this challenge. Do not write overloaded functions.

Input Format

The locked Solution class in your editor will pass different types of arrays to your printArray function.

Constraints

You must have exactly 1 function named printArray.

Output Format

Your printArray function should print each element of its generic array parameter on a new line.

Generics Solution in Java

import java.util.*;

class Printer <T> {
        public static <E> void  printArray(E[] generic){
        for(E element: generic){
  System.out.println(element);
        }
    }
}
public class Generics {

    public static void main(String args[]){
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        Integer[] intArray = new Integer[n];
        for (int i = 0; i < n; i++) {
            intArray[i] = scanner.nextInt();
        }

        n = scanner.nextInt();
        String[] stringArray = new String[n];
        for (int i = 0; i < n; i++) {
            stringArray[i] = scanner.next();
        }
        Printer<Integer> intPrinter = new Printer<Integer>();
        Printer<String> stringPrinter = new Printer<String>();
        intPrinter.printArray( intArray  );
        stringPrinter.printArray( stringArray );
        if(Printer.class.getDeclaredMethods().length > 1){
            System.out.println("The Printer class should only have 1 method named printArray.");
        }
    }
}

If you have any doubts regarding this problem or need the solution in other programming languages then leave a comment down below .

Tip: try to solve the problem yourself before reading the solution. Use the code as a reference to check your approach, and make sure you understand why it works.

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